Meteor Showers

Major Yearly Meteor Showers

Table Notes:
Peak Date is when you can expect to see the maximum number of meteors per hour from the shower.
Date Range shows the length of time, usually from a few days up to a few weeks, when you can see meteors from the shower.
No. per Hour indicate the number of meteors you can expect to see each hour providing you can see the entire sky with no trees or houses in the way.
Associated Comet is the name of the comet that produces the shower (if known).

Of those not listed I mention the following, with their peak dates, only because of their great names: Omicron Draconids (10th Oct), Giacobinids (Oct 8th), Puppids-Velids (Dec 9th & 26th) and the Omega Equulids (Feb 6th).

Of those that are listed, one of the finest displays of the year is the August Perseids. You are always guaranteed a good number of meteors - in this case around seventy-five per hour. So if it's clear on the night of the 11th / morning of the 12th August fill a flask with tea, plant a deck chair in the garden, and watch the skies. The Geminids give a good display as well, but December is not as warm for sitting outside - Brrrr!

What are Shooting Stars?

"The Solar System is a busy place. As well as the nine planets there are eighty or so moons, and many thousands of asteroids. Then there are comets, and associated with these are tiny particles each as small as a grain of sand which, despite their size, generate the most spectacular sights in the night sky. If they happen to come in contact with the Earth's atmosphere they burn up and the resulting trail we see as a streak across the sky known as a shooting star or a meteor."

Many of you will have been out on a dark and clear night (some of you, I believe, only come out then, but that's another story) and made a wish after seeing a shooting star believing they are a rare occurrence. In act, these small grains are hitting the atmosphere all the time. There is plenty of this material hurtling through space, so if you gaze up into a clear night sky for any length of time you should be rewarded with a meteor.

The tiny particles are known as meteoroids. They hit our upper atmosphere at about 65 km per second. The trail we see is between 80 km and 160 km above our heads and usually lasts considerably less than a second.

So how many can you expect to see each night? Well, with clear skies and a good low horizon an average number is five meteors per hour. As I mentioned before there are many grains hitting the atmosphere all the time, up to 100 million each day in fact, but the majority are too small to cause a meteor you can see. Of course, many arrive during daytime when there is virtually no chance of seeing them.

So we can see five on an ordinary night. Some of these streaks were caused by particles which were just aimlessly flying through space. Then along came the Earth and SMASH! - a meteor. The name we give to these is sporadic meteors because we cannot predict when they will occur. But there are swarms of particles out there orbiting the sun that give rise to annual Meteor Showers which we can predict.

During occasions throughout the year we can see a dramatic increase in the number of meteors, may be one hundred per hour or more. These Showers also appear from the same point in the sky, known as the Radiant. Simply, each shower takes its name from the constellation where the radiant is located. For instance, in April there is a Radiant in the constellation of Lyra, so the shower is called the Lyrids (see diagram).

Watching a meteor shower will generally provide you with many more meteors per hour, plus you know when they will occur and where they'll be coming from - this is all very handy. Meteor showers are where the association with comets enters the picture. For as comets fly through space they leave a trail of debris orbiting the sun - these are the meteoroids, and as the earth enters this debris a meteor storm results. This was worked out by using observers at different locations and radar to calculate the orbits of these meteors before they hit the Earth. The results, because of a resemblance of these orbits to periodic comets, strongly suggest that meteoroids had their origins in the gradual decay of such comets.

The most powerful display in recent history came from the Leonids (from Leo the Lion), on 17 November 1966, when over two thousand meteors per minute occurred at the peak of activity. This shower is associated with Comet Temple-Tuttle which has a period of 33 years. It last flew past us in February 1998, but was only visible using binoculars. With Temple-Tuttle the meteoroids are all bunched up in one part of the orbit directly behind the comet, and this is why good displays only occur about every 33 years. The return in November 1999 was watched with great interest, and indeed a storm reaching 5000 meteors per hour was recorded. Unfortunately not from most of Britain, which suffered from a large blanket of cloud. Nothing unusual there.

The Moon can play an annoying part as far as the seeing of individual meteors is concerned. The brighter the Moon, the more the sky is washed with reflected light, hence, the more 'shooting-stars' become smothered and invisible.

If you want to do a meteor shower watch that will be of use to someone, note down the following: the date including the year, the time you start and finish (in GMT) observing, the faintest magnitude you can see, the magnitude of each meteor, whether it's part of the shower or a sporadic, how much of your horizon is obscured, and for super efficiency, where each meteor trail started and finished.

Let me finish by saying that meteor showers have nothing to do with meteorites. Shooting stars are the dusty bits from comets, whereas meteorites are stony and come mainly from the asteroid belt.

Good luck, you should be making at least five wishes an hour. If you're very lucky you could be making over one hundred!

© Anton Vamplew 2008